Fire-Rated Materials for San Diego Homes
Non-combustible, ignition-resistant, and rated products, and what the labels actually mean.
The material a home is built from decides how easily an ember can start it. In a High or Very High Fire Hazard Severity Zone, the materials on your roof, walls, deck, and vents are not a style choice. They are what stands between an ember and ignition.
One quick call and we can help you sort out what your home actually needs.
The Material Decides Whether an Ember Catches
Wind-driven embers land on and against a house by the thousands. Whether they fizzle out or start a fire comes down to what they land on. A rated material buys you the one thing that matters in an ember storm: it does not ignite.
- Non-combustible materials do not burn (ASTM E136)
- Ignition-resistant materials resist catching under a sustained flame, tested after weathering (2025 CWUIC §503.2)
- Fire-retardant-treated wood is wood treated to slow ignition (California Building Code §2303.2)
- Combustible materials carry no rating and are not a code method for the rated components
“The material decides.”An ember lands the same on every home. What it lands on decides whether you have a scorch mark or a fire.
Four Classes, Highest to Lowest
Fire performance sits on a ladder. The rated parts of a home want the top of it. Here is what each class means and how it is proven.
Non-combustible
Does not burn. Proven by passing ASTM E136. Brick, stone, concrete, and steel sit here. This is the top of the ladder.
Ignition-resistant
Resists catching under a sustained flame. To qualify, a product passes an extended 30-minute flame test (ASTM E2768, which builds on ASTM E84), is tested front and back, holds up after accelerated weathering (ASTM D2898), and is listed and labeled by the State Fire Marshal (2025 CWUIC §503.2; standards of quality §503.3).
Fire-retardant-treated wood
Wood pressure-treated with fire retardant to meet California Building Code §2303.2. Approved products and manufacturers exist. It is still wood, so whether it meets your own wildfire expectations is a personal call.
Combustible
Everything with no rating: untreated wood, standard plastics, most off-the-shelf materials. Fine in much of a home, but not an accepted choice for the rated components in a High or Very High zone.
Where the class ladder applies. The code sets a material bar assembly by assembly (2025 CWUIC, Chapter 5, §504). The ones that decide a home: the roof, a Class A assembly (§504.2); exterior walls, a qualifying method from foundation to roof (§504.5); decks and other projections (§504.7); vents (§504.10); enclosed eaves (§504.3); windows and glazing (§504.8); and exterior doors (§504.9). If you are building or renovating in a High or Very High Fire Hazard Severity Zone, for the work the code covers these are requirements, not options (§101.3.1).
The Costliest Material Mistake Is Buying the Wrong One, and Doing Work Twice.
The wrong siding, an unrated deck board, a vent that suffocates the house. An assessment up front tells you which class each part of your home needs before you spend.
Flame Spread, and the Two Meanings of Class A
Most material labels report a flame-spread index from ASTM E84. Lower is better.
Class A · 0 to 25
The slowest to spread flame. What the rated parts of a home should aim for.
Class B · 26 to 75
Moderate. Acceptable in some places, not the target for high-exposure components.
Class C · 76 to 200
Fast to spread. Not appropriate for the rated components of a home in a High or Very High area.
Class A is not the whole WUI test. A WUI ignition-resistant material has to reach Class A flame spread and pass the extended 30-minute version of the test (ASTM E2768) after weathering, then carry a State Fire Marshal listing. A Class A label alone does not make a material WUI-rated.
Class A means two things. There is Class A flame spread, the ASTM E84 range above, and there is a Class A roof, which is a whole-assembly rating from a different test (ASTM E108 / UL 790). A roof is called Class A because the assembly passed that roof test, not the flame-spread scale. Roofs in the rated zones need to be Class A.
Home Hardening Is Not Standard Construction
A listed material installed wrong still lets fire in. Hardening is as much about the install as the product: gaps sealed, mesh at the right opening size, flashing where surfaces meet, no opening an ember can find.
The code carries installation standards, not just material ratings (2025 CWUIC Chapter 5; §504), and a crew that treats hardening like ordinary construction misses them.
“Home hardening is not standard construction.”The same way defensible space is not standard landscaping. The rating on the box is only as good as the install around it.
The Traps and the Words That Get Mixed Up
A few things trip up homeowners and contractors alike.
The Listing Is the Proof
A product earns its class through its State Fire Marshal listing, not a brochure claim. If it is not listed, it is not proven (2025 CWUIC §503.3.3).
Coatings Are Not a Method
Field-applied fire-retardant paints and coatings are not an accepted way to give a material its class (2025 CWUIC §503.2.5).
“Fire-Resistant” Is Loose
It is a marketing word, not a code tier. It does not mean non-combustible or the code’s ignition-resistant standard.
“Fireproof” Is Not Real
Nothing truly is. These ratings resist ignition. They do not guarantee a home survives.
Class A, Again
Remember it means two different things: a flame-spread class and a roof-assembly rating.
How to Check a Product, and Where We Come In
Every listed product is in the State Fire Marshal’s Building Materials Listing. You can search it yourself: the live Building Materials Listing tool, which is updated more often than the annual PDF. Search by product or category and confirm the listing before you buy or hire.
The hard part is usually getting the products. Most fire-rated materials are not on a big-box shelf. A lot is only available through distributors or direct from manufacturers, and sorting out what actually qualifies takes time.
Where We Help
We keep samples across the main types, siding, decking, vents and meshes, treated wood, and roofing, we are always adding to them, and on an assessment we read your materials against the code so you are not sourcing blind. Want to see a specific product? Call or text and we will show you what we have.
Related Services and Pages
Materials connect to nearly every part of home hardening. Here are the most common next steps.
Cal Wildfire Defense provides non-regulatory wildfire risk assessments and mitigation support. We do not perform official CAL FIRE inspections or issue regulatory approvals.
See Where Your Materials Stand.
Materials get their deepest look in a Home Hardening assessment, where each component is checked against the code and the right class. A Risk Walk is the fastest way to start, and you will know what your home actually needs before you spend on it.